Recently, wireless (non-contact) power transmission techniques, which do not require physical connection such as plug connection, have been used in order to make charging work easy when charging a secondary battery (hereinafter, simply referred to as a “motive power battery”) provided in, for example, a plug-in hybrid car (PHEV), an electric car (EV) and the like.
For example, in a power supply system disclosed in Patent Literature 1, one of a pair of coils electromagnetically resonate with each other is installed on a ground surface of a supply equipment. The other one is mounted to a vehicle such that power is supplied in a non-contact manner from the coil installed on the ground surface of the power supply equipment to the coil mounted to the vehicle.
In general, the coil is housed inside a case together with various types of parts such as a capacitor, configured to adjust a resonant frequency, in order to acquire reduction in size. However, the conventional power supply system has a problem that temperature inside the case rises so that power transmission efficiency decreases due to an increase in resistance value of the coil or the temperature exceeds an upper limit value of use temperature of the capacitor.
Thus, it is considered countermeasures to lower a power output by providing the capacitor away from the coil or adding a heat dissipation member in order to solve the above-described problem, but such countermeasures cause a new problem that charging time is extended due to an increase in size, an increase in weight, and reduction in transmitted power.